Implement WaitableEvent and WorkerTaskPool for multi-threaded tasks

This patch adds the basic implementation of WaitableEvent and
WorkerTaskPool for multi-threaded tasks in Dawn (for example, the
multi-threaded implementation of CreateReady*Pipeline()).

BUG=dawn:529
TEST=dawn_unittests

Change-Id: Ibf84348f4c0f0d26badc19ae94cd536cef89d084
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/36360
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Commit-Queue: Jiawei Shao <jiawei.shao@intel.com>

src/common/BUILD.gn

@@ -171,6 +171,7 @@ if (is_win || is_linux || is_chromeos || is_mac || is_fuchsia || is_android) {
       "Math.cpp",
       "Math.h",
       "NSRef.h",
+      "NonCopyable.h",
       "PlacementAllocated.h",
       "Platform.h",
       "RefBase.h",

src/common/CMakeLists.txt

@@ -33,6 +33,7 @@ target_sources(dawn_common PRIVATE
     "Math.cpp"
     "Math.h"
     "NSRef.h"
+    "NonCopyable.h"
     "PlacementAllocated.h"
     "Platform.h"
     "RefBase.h"

src/common/NonCopyable.h

@@ -0,0 +1,32 @@
+// Copyright 2021 The Dawn Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef COMMON_NONCOPYABLE_H_
+#define COMMON_NONCOPYABLE_H_
+
+// NonCopyable:
+//   the base class for the classes that are not copyable.
+//
+
+class NonCopyable {
+  protected:
+    constexpr NonCopyable() = default;
+    ~NonCopyable() = default;
+
+  private:
+    NonCopyable(const NonCopyable&) = delete;
+    void operator=(const NonCopyable&) = delete;
+};
+
+#endif